1. Field of the Invention
The present invention relates to a method of learning the full-closed position of an accelerator pedal disposed in a vehicle, and an apparatus for the same.
2. Description of the Related Art
The driver regulates the output of a vehicle via an accelerator pedal during a drive of the vehicle. It is accordingly required for an accelerator opening sensor or a throttle opening sensor, which measures the depression amount of the accelerator pedal, to transmit an appropriate required output value corresponding to a driver""s depression amount of the accelerator pedal. In the case where some required output value is transmitted from the accelerator opening sensor while the driver""s depression amount of the accelerator pedal is equal to zero, the vehicle is undesirably accelerated, regardless of the driver""s requirement to maintain the current vehicle speed or to even reduce the vehicle speed. The learning technique has accordingly be proposed to change a reference output value of the accelerator opening sensor corresponding to the depression amount of zero (that is, a full closed position of the accelerator pedal) to a more appropriate value.
The prior art technique learns the reference output value of the accelerator opening sensor on the premises that an idle switch is set ON and that the output value of the accelerator opening or throttle opening is stable. This arrangement may cause the reference output value of the accelerator opening sensor to be changed while the depression amount of the accelerator pedal is not equal to zero. In other words, this arrangement may cause the full closed position of the accelerator pedal to be mistakenly learnt. The prior art technique sets a processed value obtained by leveling the difference between a current reference output value and a newly determined reference output value or another processed value obtained by adding or subtracting a predetermined value to or from the current reference output value to the target reference output value of the accelerator opening sensor. This does not always set the optimum value to the target reference output value of the accelerator opening sensor and thereby has a relatively low learning accuracy.
The object of the present invention is accordingly to provide a technique that effectively prevents a full closed position of an accelerator pedal from being mistakenly learnt and quickly changes a current full closed position of the accelerator pedal to a new, more appropriate full closed position, thus enabling the full closed position of the accelerator pedal to be learnt with a high accuracy.
At least part of the above and the other related objects is attained by a method of learning a full-closed position output value at a full closed position of an accelerator pedal disposed in a vehicle. Here the accelerator pedal enables a required output value to be output to a driving power source of the vehicle in a continuously variable manner and has the full closed position that corresponds to a required output value of 0. The method includes determining whether an output value of the accelerator pedal has exceeded a first threshold value; determining whether the output value of the accelerator pedal is less than a second threshold value, which is smaller than the first threshold value, after the output value of the accelerator pedal has exceeded the first threshold value; when it is determined that the output value of the accelerator pedal is less than the second threshold value, determining whether the output value of the accelerator pedal is converging; and when it is determined that the output value of the accelerator pedal is converging, changing the full-closed position output value to a new full-closed position output value by taking into account the converged output value of the accelerator pedal.
This method of the present invention varies the full-closed position output value by taking into account the converged output value of the accelerator pedal, when it is determined that the output value of the accelerator pedal has exceeded the first threshold value and that the output value of the accelerator pedal is converging. This arrangement effectively prevents the full closed position of the accelerator pedal from being mistakenly learnt and quickly changes the current full closed position of the accelerator pedal to a new, more appropriate full closed position, thus enabling the full closed position of the accelerator pedal to be learnt with a high accuracy. Here the first threshold value is close to a relatively high output value corresponding to a frequently used accelerator position, whereas the second threshold value is close to an output value corresponding to the full closed position of the accelerator pedal.
In accordance with one preferable application of the method of the present invention, determining whether the output value of the accelerator pedal is converging is carried out when the output value of the accelerator pedal monotonously decreases. In accordance with another preferable application of the method of the present invention, determining whether the output value of the accelerator pedal is converging is carried out when a current full-closed position output value is greater than a currently observed output value of the accelerator pedal. Determining whether the output value of the accelerator pedal is converging is carried out on the condition that the output value of the accelerator pedal monotonously decreases, when the current full-closed position output value is not greater than the currently observed output value of the accelerator pedal.
In accordance with one embodiment that attains either one of the above preferable applications, it is determined that the output value of the accelerator pedal monotonously decreases when an absolute difference between a currently observed output value of the accelerator pedal and a previous output value of the accelerator pedal is within a preset range and when a future output value of the accelerator pedal after elapse of a predetermined time period is smaller than the currently observed output value of the accelerator pedal. This arrangement enables learning to be performed even when minute peaks appear due to a simple noise, thus increasing the frequency of learning and enhancing the learning effects. Here the predetermined time period is longer than a sampling time required to detect a variation in output value of the accelerator pedal and is suitable to specify the general characteristics of the output value of the accelerator pedal. In accordance with another embodiment that attains either one of the above preferable applications, it is determined that the output value of the accelerator pedal monotonously decreases when the currently observed output value of the accelerator pedal is smaller than the previous output value of the accelerator pedal. In this embodiment, the continuous decrease in output value of the accelerator pedal is required for the determination that the output value of the accelerator pedal monotonously decreases. Namely learning is not performed when any peak appears due to a noise. This arrangement effectively prevents the full closed position of the accelerator pedal from being mistakenly learnt. In this arrangement, the term xe2x80x98monotonous decreasexe2x80x99 is not restricted to the strict sense that does not allow any increasing variation but means a substantially monotonous decrease that allows minute increasing variations, for example, due to the noise.
In the method of the present invention, it may be determined that the output value of the accelerator pedal is converging when a variation in output value of the accelerator pedal is within a predetermined range. This arrangement enhances the speed of determination with regard to the convergence of the output value of the accelerator pedal.
In the method of the present invention, it may be determined that the output value of the accelerator pedal is converging when the currently observed output value of the accelerator pedal is either identical with the previous output value of the accelerator pedal or less than the previous output value of the accelerator pedal by a predetermined rate. This arrangement does not allow learning to be performed when any peak appears due to a noise, thus effectively preventing the full closed position of the accelerator pedal from being mistakenly learnt due to the noise. In accordance with one preferable embodiment of the method of the present invention, when a current full-closed position output value is greater than the converged output value of the accelerator pedal, a remainder obtained by subtracting a predetermined value from the current full-closed position output value is set to the new full-closed position output value.
In accordance with another preferable embodiment of the method of the present invention, when a current full-closed position output value is not greater than the converged output value of the accelerator pedal, a sum obtained by adding a predetermined value to the current full-closed position output value is set to the new full-closed position output value. In this embodiment, when the convergence of the output value of the accelerator pedal continues for a predetermined time period, the converged output value of the accelerator pedal is set to the new full-closed position output value. This arrangement quickly sets the actual full closed position of the accelerator pedal to the new full-closed position output value, thus enhancing the learning accuracy.
In accordance with still another preferable embodiment of the method of the present invention, when a current full-closed position output value is not greater than the converged output value of the accelerator pedal, the converged output value of the accelerator pedal is set to the new full-closed position output value. This arrangement quickly sets the actual full closed position of the accelerator pedal to the new full-closed position output value, thus enhancing the learning accuracy. In accordance with another preferable embodiment of the method of the present invention, the output value of the accelerator pedal is expressed by an accelerator opening that is related to a depression amount of the accelerator pedal, the accelerator opening being a predetermined percent at a maximum output value of the accelerator pedal and being zero percent at a minimum output value of the accelerator pedal. In accordance with still another preferable embodiment of the method of the present invention, the output value of the accelerator pedal is expressed by a throttle opening that is related to a depression amount of the accelerator pedal, the throttle opening being a predetermined percent at a maximum output value of the accelerator pedal and being zero percent at a minimum output value of the accelerator pedal. Here the predetermined percent represents a preset accelerator opening or throttle opening that is assured even after the accelerator pedal has undergone a time variation, for example, a value in a range of approximately 55% to 70%.
In accordance with another preferable application of the present invention, the method further includes the step of: informing a driver of occurrence of an abnormality on the accelerator pedal when the new full-closed position output value is smaller than the second threshold value but greater than a third threshold value, which is smaller than the second threshold value and corresponds to a mechanical full closed position of the accelerator pedal. This arrangement efficiently detects an abnormality of the accelerator pedal and informs the driver of occurrence of the abnormality in the course of learning the full closed position of the accelerator pedal.
The present invention is also directed to a method of successively updating a full-closed position output value of an accelerator pedal at a full closed position corresponding to a specific state in which an operating quantity of the accelerator pedal is equal to zero. The method includes the steps of: determining whether an output value of the accelerator pedal is less than a threshold value; when it is determined that the output value of the accelerator pedal is less than the threshold value, determining whether the output value of the accelerator pedal is converging; when it is determined that the output value of the accelerator pedal is converging, comparing a current full-closed position output value of the accelerator pedal with the converged output value of the accelerator pedal; when the current full-closed position output value of the accelerator pedal is greater than the converged output value of the accelerator pedal, setting a mean of the current full-closed position output value of the accelerator pedal and the converged output value of the accelerator pedal to a new full-closed position output value of the accelerator pedal; and when the current full-closed position output value of the accelerator pedal is not greater than the converged output value of the accelerator pedal, setting the converged output value of the accelerator pedal to the new full-closed position output value of the accelerator pedal.
This updating method of the present invention sets the converged output value of the accelerator pedal to the new full-closed position output value of the accelerator pedal when the current full-closed position output value of the accelerator pedal is not greater than the converged output value of the accelerator pedal. This arrangement enhances the learning accuracy at least in a range of high output values of the accelerator pedal.
In accordance with one preferable application of the updating method of the present invention, when the current full-closed position output value of the accelerator pedal is not greater than the converged output value of the accelerator pedal, the mean of the current full-closed position output value of the accelerator pedal and the converged output value of the accelerator pedal is set to the new full-closed position output value of the accelerator pedal. When a convergence time period, in which the output value of the accelerator pedal converges, exceeds a preset time period, the converged output value of the accelerator pedal is set to the new full-closed position output value of the accelerator pedal. This arrangement effectively prevents the full closed position of the accelerator pedal from being mistakenly learnt, while enhancing the learning accuracy at least in a range of high output values of the accelerator pedal.
In the updating method, the output value of the accelerator pedal may be obtained as either one of an accelerator opening or a throttle opening that is related to a depression amount of the accelerator pedal.
The present invention is further directed to a full-closed position learning apparatus that learns a full closed position of an accelerator pedal in a released state. More specifically the full-closed position learning apparatus outputs a depression amount of the accelerator pedal as an accelerator opening and learns the accelerator opening at the full closed position of the accelerator pedal, which has the full closed position corresponding to a depression amount of zero. The full-closed position learning apparatus includes: an accelerator depression measurement unit that measures a depression amount of the accelerator pedal as an operational opening; a first storage unit that registers therein an accelerator open record when the observed operational opening exceeds an open record reference value; a learning permission decision unit that determines whether the observed operational opening is less than a learning permission reference value, which is smaller than the open record reference value; an opening convergence decision unit that determines whether the operational opening is converging when it is determined that the observed operational opening is less than the learning permission reference value while the accelerator open record is present in the first storage unit; and a full-closed position opening variation unit that varies the operational opening at the full closed position to a new full-closed position operational opening by taking into account the converged operational opening, when it is determined that the operational opening is converging.
The full-closed position learning apparatus of the present invention varies the operational opening at the full closed position to the new full-closed position operational opening by taking into account the converged operational opening, when it is determined that the observed operational opening is less than the learning permission reference value while the accelerator open record is present in the first storage unit and that the operational opening is converging. This arrangement effectively prevents the full closed position of the accelerator pedal from being mistakenly learnt and updates the current full-closed position operational opening to a new, more appropriate operational opening.
In accordance with one preferable embodiment of the present invention, the full-closed position learning apparatus further includes a decreasing state decision unit that determines whether the operational opening monotonously decreases, when the accelerator open record is present in the first storage unit. In this embodiment, the opening convergence decision unit carries out the determination of whether the operational opening is converging when it is determined that the operational opening monotonously decreases.
In the above preferable embodiment, the decreasing state decision unit may determine that the operational opening monotonously decreases when an absolute difference between a currently observed operational opening and a previous operational opening is within a preset range and when a future operational opening after elapse of a predetermined time period is smaller than the currently observed operational opening. Here the predetermined time period is longer than a sampling time required to detect a variation in operational opening and is suitable to specify the general characteristics of the operational opening. In the above preferable embodiment, the decreasing state decision unit may alternatively determine that the operational opening monotonously decreases when a currently observed operational opening is smaller than a previous operational opening. In accordance with one preferable application of the full-closed position learning apparatus, the opening convergence decision unit determines that the operational opening is converging when a variation in operational opening is within a predetermined range.
In accordance with another preferable application of the full-closed position learning apparatus, the opening convergence decision unit determines that the operational opening is converging when a currently observed operational opening is either identical with a previous operational opening or less than the previous operational opening by a predetermined rate. In accordance with still another preferable application of the full-closed position learning apparatus, the full-closed position opening variation unit sets a remainder obtained by subtracting a predetermined value from a current full-closed position operational opening to the new full-closed position operational opening, when the current full-closed position operational opening is greater than the converged operational opening.
In accordance with another preferable application of the full-closed position learning apparatus, the full-closed position opening variation unit sets a sum obtained by adding a predetermined value to a current full-closed position operational opening to the new full-closed position operational opening, when the current full-closed position operational opening is not greater than the converged operational opening. In this application, the full-closed position opening variation unit sets the converged operational opening to the new full-closed position operational opening when the convergence of the operational opening continues for a predetermined time period.
In accordance with still another preferable application of the full-closed position learning apparatus, the full-closed position opening variation unit sets the converged operational opening to the new full-closed position operational opening when a current full-closed position operational opening is not greater than the converged operational opening.
In one preferable embodiment of the present invention, the full-closed position learning apparatus further includes: an accelerator abnormality decision unit that compares the new full-closed position operational opening with the learning permission reference value and with a mechanical full closing value, which is smaller than the learning permission reference value and corresponds to a mechanical full closed position of the accelerator pedal; and an information unit that informs a driver of occurrence of an abnormality on the accelerator pedal when the new full-closed position operation opening is smaller than the learning permission reference value but is greater than the mechanical full closing value. This arrangement enables an abnormality of the accelerator pedal to be detected, simultaneously with learning the full closed position of the accelerator pedal.
In the full-closed position learning apparatus of the present invention, the accelerator depression measurement unit may be an accelerator opening sensor that measures the depression amount of the accelerator pedal as an accelerator opening, or may alternatively be a throttle opening sensor that measures an operation amount of a throttle value, which works in combination with an operation of the accelerator pedal, as a throttle opening. In either case, the depression amount of the accelerator pedal can be obtained.
The full-closed position learning apparatus exerts the essentially equivalent functions and effects to those of the learning method of the present invention discussed above, while attaining the individual functions and effects by means of each individual constituent of the apparatus.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.